The threat has remained largely theoretical ever since a spa in Alexandria, Va., brought the fishy foot treatments to U.S. shores in 2008 as a replacement for the razors typically used to scrape dead skin from calloused toes and heels. More than 6,000 patrons flocked to the spa in its first five months for a fish pedicure. But U.S. and British health officials continue to warn that anyone with open sores or skin cuts, an underlying medical condition such as diabetes or an immune system compromised by AIDS, cancer or advanced age should steer clear of a fish pedicure.

“The most important thing to stress at this point is that the U.K. Health Protection Authority considers the human health risks to be very low, and we would not want your readers to be unduly alarmed by our findings,” David W. Verner-Jeffreys, lead author of the new report, told ABC News Tuesday.

Scientists began to get indications of the kinds of microbes that could be bathing fish spa patrons’ feet in April 2011, when British authorities investigated a reported bacterial outbreak among 6,000 Garra rufa fish imported from Indonesia to British salons and pedicure spas. Tests revealed the fish had been infected with Streptococcus agalactiae, group B Streptococcus, bacteria that can cause pneumonia and serious infections of the bones, joints and blood in people of all ages and life-threatening infections in newborns.

The bacteria findings appear Wednesday in Emerging Infectious Diseases, a journal published by the federal Centers for Disease Control and Prevention in Atlanta, which has been monitoring health effects associated with fish pedicures.

More than 10 states have banned the practice for a variety of reasons, the CDC said, including the inability to sufficiently clean fish pedicure tubs between patrons; the impossibility of disinfecting or sanitizing live fish; regulations that specify fish in a salon must be kept in an aquarium, and a humanitarian justification that to entice the fish to feed on dead human skin, they must be starved, “which might be considered animal cruelty.”

In the United States, “there have been no published reports to date regarding illness from fish pedicures,” the CDC said in a June 2011 document. “However, fish-free foot-baths in nail salons have been implicated in several outbreaks of nontuberculous mycobacterial infections, including the species Mycobacterium abscessus and M. fortuitum,” which have left customers with boils and scars.